Check the size of the ground that is bonding the tub. I can't tell you how many times I've seen hackers out there use a #10 or even #12 ground. Darn near every modern hot tub needs a #6 ground (assuming 50A being brought in over 3 #6 wires). Obviously the GFCI is not working properly either (one could argue that the tingle isn't enough to trip it I suppose -- heck, a lot of hackers ignore the GFCI with the thought that "hey, it works without it"). The most glaring issue here is that there is a loose hot wire that is shorted to a metal water pipe, thus energizing the water (I'm assuming that the tingle is felt when she is making contact with the water).
